Hi JulianR,
Thanks for getting back to me here. There currently isn't a way to record the purchase taxes separately in QuickBooks Online. If you'd like to see this available in product updates, you can submit a suggestion to our Development Team. Recommendations are greatly appreciated to improve your overall customer experience with QuickBooks Online. In the interim, you can have a look at third party apps for the best fit for your business needs. I hope you find this to be helpful.
If there's anything else we can help you with, feel free to reach out. We're here for you!
